The overarching aim of this Independent Scientist Award (K02) application is to develop skills in genetics and epidemiology, and enhance my expertise in quantitative methodology pertaining to substance use disorder (SUD) etiology. The goal of the research program in the next five years is to integrate statistical and psychometric methods for deriving a practical and valid assessment of SUD liability. Employing item response theory, in conjunction with longitudinal multivariate modeling, the product of the proposed research is a continuous scale that quantifies individual risk for SUD at ages 10-12, 16, 19, and 22. This scale will be a provisionally validated self-administered questionnaire that can be used in routine assessment of youth and young adults for identifying those in need of intervention. Two versions will be developed and compared: paper and pencil for group screening and computer adaptive testing for individual assessment. To achieve this project goal, I will access the Center for Education on Drug Abuse Research (CEDAR) database consisting of multidisciplinary protocols for measurement of SUD risk. In this center grant, where I direct the Methodology and Statistics Core, psychological and environmental risk factors are prospectively studied from childhood to adulthood. The education and training component will prepare me for an R01 that is directed at standardizing the SUD liability scale derived in this research in the context of a genetic epidemiological paradigm. In this manner, etiology from the standpoint of gene-environment interactions will be investigated using the SUD liability scale provisionally derived in this project and simultaneously standardized for practical application. The long-term career goal will thus be to apply my psychometric and statistical expertise to develop instrumentation that clarifies SUD etiology and conjointly has practical utility.